JP2018512611A - Light beam forming apparatus and spotlight using the light beam forming apparatus - Google Patents

Abstract

The present invention provides a light beam shaping device, for example for use as part of a spotlight. The collimator is for receiving light from a light source and providing a more collimated output. The optical plate is provided at the output of the collimator, has an array of lenses on the input side, and has an array of lenses corresponding to the output side on the opposite side. The lens is configured as a pair of Koehler lenses, and at least some of the output lenses are tilted with respect to the overall plane of the optical plate. This tilt provides a design option to improve beam shaping characteristics.

Description

  In particular, the present invention relates to a light beam shaping apparatus that is used for an illumination unit for adjusting the characteristics of a spotlight beam, but is not limited thereto.

  In particular, it is well known that designing systems or optical components for spot lighting effects is generally difficult for light sources that are not perfectly uniform over the angle or position in the light output of the light source.

  There are many known available light sources, for example, LEDs can be grouped into high power LEDs, medium power LEDs, low power LEDs, cluster LEDs and chip on board.

High power LEDs can be dimensionally small, for example, having an area of about 1 mm ² , and the LED phosphor can be well matched to the area of the chip. This results in a light distribution with a uniform color relative to the radiation angle.

Medium and low power LEDs are often somewhat larger, for example having an area of ² to 6 mm ² . This use of medium or low power LEDs often results in color dispersion. This is because these LEDs have the disadvantage that they emit light in all directions and their color is not uniform across the LEDs.

  Beam shaping is found in most lighting applications. Beam shaping optics include, for example, reflectors and collimators, which are used in most luminaires.

  The problem of chromatic dispersion is exacerbated when using medium power light emitting diodes (LEDs) to generate white light or when using red, green and blue (RGB) LEDs to generate color tunable light. Even when such a light source is combined with an optical component having collimation characteristics, a chromatic dispersion effect on the radiation angle can occur. This is a well-known big problem and often prevents the use of medium power LEDs.

  When using LEDs in spotlight applications, a collimated beam is desirable and the color should be uniform across the spot.

  A well-known solution for creating a collimated uniform color beam from a divergent source with color non-uniformity is to first collimate the light with a collimator, This is by mixing colors using Koehler lens design.

  The Kohler design consists of a double lens array with one array on each side of the substrate, and the two arrays together form an optical plate. Both lens arrays are located at the focal planes of each other and aligned with respect to each other. The function of each Koehler lens pair is to redistribute the light entering the first surface of the substrate so as to remove the angle information of the original beam spot.

  Even if a collimator and an optical plate are used, it is difficult to control the output beam shape to have a desired intensity characteristic.

  The invention is defined by the claims.

According to an example according to an aspect of the invention,
A collimator for receiving light from a light source and providing a more collimated output;
An optical plate for receiving the more collimated output, the optical plate having a two-dimensional array of lenses on the input side and a two-dimensional array of lenses corresponding to the opposite output side A molding device,
Each of the input side lenses has a focus on the corresponding lens on the output side, and each of the output side lenses has a focus on the corresponding lens on the input side, and at least some of the output side lenses. However, a light beam shaping device is provided that is inclined with respect to the general plane of the optical plate.

  The optical plate functions like an array of Kohler lens pairs. The inclination of the lens on the output side of the optical plate is used as a design parameter for adjusting the beam shaping characteristics of the optical plate. Specifically, the tilt adds a diffusing function to the color mixing function of the pair of lenses in the Kohler. The two-dimensional array is a grating of lenses, each defining a grating of lenses arranged at the position of the lens itself on the optical plate.

  The inclination of at least some of the lenses is, for example, an inclination toward the center or an inclination away from the center.

  The tilt provides the tilt of the optical axis of the lens with respect to the normal to the general plane of the optical plate. This tilt provides diffusion and therefore a beam expansion function.

  Individual lenses can have various shapes including concentric patterns.

  By making the array of lenses a grating, individual lenses will be assigned to non-circular local areas of the optical plate (since the circles cannot be fitted together). Individual lenses may have a truncated outline, such as a hexagonal outline (for a hexagonal grid) or a square outline (for a square grid). The diffusion provided by the tilt of the lens prevents this local end clipping of the lens shape from leading to an undesirable shape of the beam spot. In this way, the entire optical plate can be covered with a lens without the disadvantages of non-circular beam spots.

  The array of lenses can form a rotationally symmetric pattern, such as a simple honeycomb pattern. The rotationally symmetric pattern may have four or more rotationally symmetric orders (eg, a square lattice with rotational symmetry 4 or a hexagonal lattice with rotational symmetry 6). However, more complex tessellation is possible. Furthermore, not all lenses need to be the same shape, so more complex mosaics are possible, for example with 8 or 12 times symmetry.

  In order to provide these higher rotationally symmetric designs, the lenses may not be regular polygons, or there may be various polygon combinations.

  In one example, the pattern of the array of lenses may be a hexagonal grating, in which case the optical plate may guarantee a circular beam shape in the far field despite the hexagonal grating pattern. Furthermore, the angular intensity distribution can be controlled.

  The tilted lens is, for example, a base plane (perpendicular to the optical axis), and the intersection between the reference plane and the general plane of the optical plate is the center The reference plane is inclined so as to be a tangent centered at. This means that the tilt of the lens is centered on the center of the plate, i.e. the lens is tilted towards or away from the center.

  The optical axis of the inclined lens is, for example, inclined by an inclination angle with respect to the normal (in the overall plane of the optical plate), and the inclination angle is the same distance from the center. By the way, it is the same for all lenses. The optical plate is basically rotationally symmetric (having a rotationally symmetric finite order), but the design may vary with distance from the center.

  All optical axes of the tilted lens may be tilted by the same tilt angle with respect to the normal (in the global plane of the optical plate). This makes the optical plate design easy to implement. The tilt angle may vary across the optical plate, for example depending on the radius from the center.

  The tilt angle of all tilted lenses is preferably less than 40 degrees.

  The central lens is generally not tilted. All of the remaining lenses may be tilted, but it is also possible to have lenses in which the area of the optical plate is not tilted.

  The collimator may include a Fresnel lens.

The present invention
A light source;
There is also provided an illumination unit comprising an apparatus as defined above for beam shaping of light output from the light source.

  The light source preferably comprises an LED or an array of LEDs, in which case the lighting unit may comprise an LED spotlight. The spotlight uses a beam shaping device that provides a circular light intensity distribution in the far field, eg, a reflector body that houses at least some LEDs.

Examples of the present invention will now be described in detail with reference to the accompanying schematic drawings.
1 shows a known beam shaping device combining a collimator and an optical plate. A modified optical plate is shown. Fig. 2 shows how the optical plate can receive collimated light in a non-normal direction. Fig. 4 shows how the maximum allowable angle of the optical plate of Fig. 3 exists. Figure 2 shows a known optical plate and a modified optical plate superimposed. FIG. 6 is a ray diagram showing how a known optical plate processes incident collimated light. FIG. 6 is a ray diagram showing how a modified optical plate processes incident collimated light. Figure 2 shows the angular intensity function of a known illuminated optical plate. Fig. 4 shows the angular intensity function of an illuminated modified optical plate. Four possible lens array designs are shown.

  The present invention provides a light beam shaping device, for example for use as part of a spotlight. The collimator is for receiving light from a light source and providing a more collimated output. The optical plate is provided at the output of the collimator, has an array of lenses on the input side, and has an array of lenses corresponding to the output side on the opposite side. The lens forms a grating. The lenses are configured as a pair of Koehler lenses, with at least some of the output lenses tilted with respect to the general plane of the optical plate. This tilt provides a design option to improve beam shaping characteristics.

  FIG. 1 shows a known optical system that combines a collimator and an integrated plate that utilizes a pair of Koehler lenses.

  The system comprises a light source 10, for example an LED or LED array, a collimating optical element 12, in this example in the form of a collimating optical plate, and an integrated optical element in the form of a second optical plate 14.

  The light source may include one or more lighting elements. If multiple light sources are used, they may be light sources of various colors, for example. In other examples, the light source may be a single color illumination element distributed over an area, or a single color with the output beam color and direction varying as a function of position over the light output surface. One lighting element may be used.

  The collimating optical plate 12 is, for example, a Fresnel lens, which pre-collimates the light and sends it to the integrated optical plate 14. This means that light emanating from any particular point on the surface of the collimating optical plate 12 has a limited angular range that forms a beamlet, for example an angular spread of less than 10 degrees. Beamlet angular spread is defined by the distance to the source and the size of the source.

  The required degree of collimation of the incoming light up to the optical plate 14 is determined by the Kohler design, for example, the optical plate has a 20 ° allowable input angle on each side of the normal. The direction of the incoming beam is in the normal direction (perpendicular to the optical plate). If the optical plates are located immediately behind the collimator, their diameters will be approximately the same. If the optical plate is far from the collimator as shown schematically in FIG. 1, the optical plate can be larger than the collimator while maintaining the light incident on the optical plate within an acceptable angular range.

  Other lens designs may be used for the collimating function. The collimator may instead have a total internal reflection (TIR) collimator.

  The integrated optical plate uses a pair of Koehler lenses as described further below.

  The light exiting the collimating optical plate 12 has an output angle range with respect to the normal (as shown as α in FIG. 1), which is within an allowable angle of the second optical plate, for example α < β / 2, where β is the allowable angle at the output of the second integrated optical plate 14 as well as the spread of the output angle.

  The integrated optical plate 14 forms a light beam 16 from each beamlet received from the collimating optical plate 12. The light beam is centered in the normal direction. Furthermore, the light originating from the various areas of the light source 10 is preferably mixed substantially uniformly by the integrated optical plate 14 (since the light source 10 will not be a perfect point light source).

  The resulting beam output from the optical system is a superposition of the beam 16 formed by the integrated optical plate 14. Each of the beams 16 are mixed uniformly. The integrated optical plate 14 removes color artifacts based on this uniform blending.

  FIG. 2 shows in more detail the integrated optical plate 14 including the modifications according to the invention. It shows a known beam processing device that utilizes a pair of Koehler lenses modified by the introduction of tilt into some of the output lenses.

  The optical plate 14 has an upstream surface 15 on which a series of curved lens elements are distributed. This is the first surface of the optical plate that faces the light source. The curved lens element is focused on the associated opposite downstream surface 16 of the optical plate 14. This is the second surface of the optical plate facing away from the light source.

  The downstream surface 16 of the optical plate 14 is a curved lens arranged such that each of the curved lens elements on the first surface 15 has an optically aligned curved lens element associated with the second surface 16. Alternatively, it is composed of a lens element.

  Similarly, the curved lenses on the second surface 16 have their focal points located on the first surface 15. In this way, the curved lens element on the second surface 16 is configured to mix light over an angular range that follows focusing by the curved lens disposed on the first surface 15.

  FIG. 2 shows a cross-sectional view of the three lenses of the optical plate 14. The central lens is arranged on the center 25, the central point or the central axis of the general plane P of the optical plate and has no inclination. In this example, the lenses for both sides have a slope towards the center. This allows the light to be directed away from the center. The surface normal of the lens is indicated by reference numeral 17. The surface normal is the optical axis of the corresponding lens and is perpendicular to the reference plane of the lens. The inclination of the lens provides an inclination of the surface normal so that the surface normal is not parallel to the normal direction of the general plane of the optical plate 14.

  As an example, the left Köhler lens pair has a first (input) lens 18 facing the incident light from the collimator and a second (output) lens 19 facing the output region where the output beam is directed.

  The output lens 19 has a reference plane 23 that is inclined by an inclination angle γ with respect to the overall plane P of the optical plate. The example shown in FIG. 2 has an inclination angle γ of about 300.

  FIG. 2 shows the rays incident on the optical plate reaching in the normal direction. However, this is not essential. For example, if the light source has an array of LEDs, different positions of these LEDs with respect to the collimator will cause different angles of incidence of the light of the different LEDs. This is illustrated in FIG. 3, in which three different LEDs, LED1, LED2, LED3, cause illumination from a collimator that reaches the integrated optical plate at different angles of incidence.

  The lenses on the first and second surfaces may have a substantially constant radius of curvature, i.e. they may be ordinary spherical lenses centered on the symmetry axis, which is The surface normal as described with reference to FIG.

  A normal Köhler lens pair is designed for a specific divergence angle of light coming from a collimator (which is itself a function of position on the collimator). Once the thickness of the optical plate is known, the radius of the lens is determined.

  The mosaic of lens pairs that together form the optical plate is another parameter that can be selected. This determines the far-field light distribution, such as a top hat or Gaussian or hexagonal distribution.

  For proper operation of the Köhler design, the tolerance angle limits the degree of collimation of the output beam. In order to maintain the degree of collimation while uniformly mixing all incoming rays over the angular output direction, the maximum beam angle needs to be smaller than the allowable angle of the Koehler lens. A typical Kohler tolerance angle is, for example, 2 × 20 °.

  FIG. 4 shows the ray 20 of the incident beam at the maximum allowable angle of a pair of Koehler lenses. As shown, the collimated beam 20 is focused at the very edge of the opposite lens. The angle of the beam 20 is, for example, 20 ° from the normal line 22.

  In many lighting applications, a maximum beam angle above this value is desirable.

  In a normal Kohler design, the degree of collimation of incident light is maintained. However, for practical design reasons (mainly related to the size of the Koehler element), the degree of collimation allowed is limited, i.e. limited to a fairly narrow beam from an illumination point of view. The tilt used in FIG. 2 modifies the Köhler design so that the degree of collimation is not preserved, i.e., by modifying the extraction lens array, the extracted beam is broadened compared to the incident beam.

  The lens array has a two-dimensional lattice configuration. For the lattice configuration, lenses having outer shapes that fit each other, such as a rectangular lens or a hexagonal lens, are used. The lattice configuration is rotationally symmetric (having n-fold rotational symmetry of finite order n), and has, for example, a hexagonal lattice having six-fold rotational symmetry. In order to make the lens fully mosaic, the lens will have a hexagonal outline with the edges cut off. Normally, a hexagonal lens array provides a hexagonal beam spot directly in the far field, but a circular beam shape is desirable.

  A typical solution to this problem is a dedicated lens mosaic designed specifically for collimated light sources that differ from the hexagonal pattern.

  The present invention makes use of the lens tilt of the output face of the optical plate to change the beam spot shape and / or to change the beam polarization and / or to modify the selected mosaic of the lens. For example, it may be possible to achieve a circular far-field light distribution using a hexagonal lens mosaic.

  FIG. 5 shows the resulting optical plate design. FIG. 5 shows a conventional design 60 and a design 62 modified according to an example of the present invention, superimposed on each other.

  In one example, the individual lenses form a hexagonal lattice (in plan view). All of the lenses in this example are inclined away from the central axis 64. In other words, the lenses on the output surface of the optical plate are such that their reference plane is at the slope and their surface normal direction is tilted with respect to the general normal direction. It is inclined.

  As the above two examples show, the slope of this slope may be a slope toward the center of the optical plate or may be a slope away from the center of the optical plate. In any case, the surface normal may intersect the global normal of the optical plate (either above or below the optical plate depending on the tilt). The curved portion of each lens may have a certain radius of curvature and may be rotationally symmetric with respect to the surface normal direction. In order to make the tilt lens into a continuous sheet, there may be a step between the edge portions of adjacent lenses.

  The central lens is not tilted. Furthermore, the lens for the first inner radius of the optical plate may not be tilted (so that the subset of lenses is not tilted). The tilt may start at a specific radius from the center and the tilt angle may not be the same for all lenses. The radius of curvature may be the same for all lenses, but may not be the same for all lenses. Each lens has a single tilt angle value associated with it, but the tilt angle may be different if the distance from the center is different. At a given distance from the center, the tilt angle is the same for all lenses to maintain n-fold rotational symmetry of the optical plate.

  The result is preferably a rotationally symmetric configuration (having a finite order). It can be formed, for example, as a regular hexagonal array.

  FIGS. 6 and 7 show how the output beam changes when an additional 30 degree tilt is added to each of the output lenses of the Koehler lens pair. The angle of 30 degrees and the fact that the tilt is the same for all lenses is an arbitrary choice and for demonstration purposes only. The tilt angle may be different for different lenses, for example, with a tilt angle that is a function of the radial distance from the center, for example, a change in tilt angle that increases or decreases with increasing radial distance from the center. The change may be gradual or, in other examples, abrupt and significant steps.

  FIG. 6 shows the beam path when a conventional optical plate is illuminated by a fully collimated beam.

  FIG. 7 shows the beam path when the modified optical plate is illuminated by a fully collimated beam.

  There are various stray beams due to total reflection. Ignoring these stray beams, the overall optical function can be observed.

  FIG. 8 shows the spot intensity of a conventional optical plate, and FIG. 9 shows the spot intensity of the modified configuration. The graph shows intensity as a function of angle. The intensity profile indicates the intensity in an angular space having an angle from −90 degrees to +90 degrees in the horizontal and vertical directions. The cross section graph shows a horizontal cross section of intensity versus angle at a vertical angle of 0 degrees.

  The full width at half maximum (FWHM) changed from 20 degrees to 30 degrees. This shows the possibility of making the beam as wide as desired to match the desired characteristics of the spotlight.

  Color uniformity in the far field is still acceptable.

  The distance between the paired lenses on the two surfaces will match the focal length of the lens. It is another design parameter that can be used to affect optical performance.

  There is a one-to-one mapping between the lens on the first surface 15 and the lens on the second surface 16. This allows for precise control of the light output characteristics from the optical plate.

  The radii of the lenses in the array may all be the same. The tilt angle may be increased toward the edge of the optical plate. If the surface modulation height is to be fixed, the lens pitch may decrease towards the edge of the optical plate. In other examples, the tilt angle may be the same for all lenses. Furthermore, the use of a constant lens radius is not essential.

  As explained above, the lenses may be non-circular so that the lenses fit together to fill the area of the optical plate, but this is not essential. FIG. 10 shows four possible mosaics. FIG. 10A shows a mosaic of hexagonal lattice-shaped circular lenses. The circles do not fit perfectly together, so there is a gap between the lenses. FIG. 10B shows a mosaic of square lenses having a square lattice shape. FIG. 10C shows a mosaic of lenses that have hexagonal lattice shapes, with the ends cut off to form hexagons. In this case, the lens shapes perfectly fit each other. FIG. 10 (d) shows a mosaic of lenses in the form of a square lattice, with the ends cut off to form a square.

  If the tilt of the lens increases towards the edge of the lens, the tilt will reduce the horizontal (plan view) area. This can interfere with the mosaic and lead to air gaps between the lenses. The lens can also be brought closer to reduce these voids. When the top lens is brought closer, the lens on the bottom surface of the plate is changed accordingly so that the top lens and the bottom lens match in surface area.

  For best efficiency, void formation should be prevented, which can be achieved by using a lens with a shape that is a non-regular polygon.

  The invention makes it possible to use the tilt of the lens as a design parameter in order to be able to realize the desired optical function.

  The optical plate is a polymer material such as PE (polyethylene), PP (polypropylene), PEN (polyethylene naphthalate), PC (polycarbonate), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA) (Plexiglas or Perspex) From the group consisting of cellulose acetate butyrate (CAB), silicone, polyvinyl chloride (PVC), polyethylene terephthalate (PET), PETG (glycol-modified polyethylene terephthalate), PDMS (polydimethylsiloxane) and COC (cycloolefin copolymer) One or more selected materials may be included. However, there can be other polymers (copolymers). The optical plate may be made of glass.

  When used as part of a spotlight, a light beam shaping device shapes output light from an LED or LED array to produce a circular light intensity pattern at the output. The spotlight has, for example, an outer housing in which an LED or LED array and a beam shaping device are mounted. As would be well known to those skilled in the art, suitable housing electronics would also be included in the housing, for example, to convert the main power input to a DC drive signal for the LED.

  Those skilled in the art in practicing the claimed invention may understand and achieve other variations to the disclosed embodiments from a study of the drawings, the specification, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the singular form does not exclude the presence of a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims (11)

A collimator for receiving light from a light source and providing a more collimated output;
An optical plate for receiving the more collimated output, the optical plate having a two-dimensional array of lenses on the input side and a two-dimensional array of lenses corresponding to the opposite output side A molding device,
Each of the input side lenses has a focus on the corresponding lens on the output side, and each of the output side lenses has a focus on the corresponding lens on the input side, and at least some of the output side lenses. A light beam shaping device that is inclined with respect to the overall plane of the optical plate.   The apparatus of claim 1, wherein at least some of the lenses are tilted toward or away from the center.   The apparatus according to claim 1, wherein the input lens array and the output lens array have a finite rotational symmetry having a order of at least 4 with respect to a rotation center.   The apparatus of claim 3, wherein the grid pattern comprises a hexagonal grid.   The inclined lens has an optical axis that is inclined by an inclination angle with respect to a normal of the overall plane of the optical plate, and the inclination angle is the same for all lenses at the same distance from the center. The device according to claim 1, which is the same.   6. The apparatus of claim 5, wherein the tilt angle is the same for all tilted lenses.   7. A device according to any one of the preceding claims, wherein the tilt angles of all tilted lenses are less than 40 degrees.   The apparatus according to claim 1, wherein the collimator has a Fresnel lens. A light source;
An illumination unit comprising: an apparatus according to claim 1 for shaping a beam of light output from the light source.   The lighting unit according to claim 9, wherein the light source includes an LED or an array of LEDs.   11. An illumination unit according to claim 10, comprising an LED spotlight, wherein the device provides a circular light intensity distribution in the far field.

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